problem

I was working on one of my new projects and trying to build my Unity project for WebGL, but when I clicked

solution

UnityHub makes installing new modules super easy!

• Open up UnityHub
• Go to Installs
• Click the hamburger button (the three dots in the top right corner) of the Unity install you want to add the WebGL module to
• Select Add Modules
• Select the WebGL Build Support module
• wait for it to finish downloading and installing

Profit!